/Engine/Plugins/FX/Niagara/Source/Niagara/Classes/NiagaraEffectType.h
Significance is determined by the system's distance to the nearest camera. Closer systems are more significant.
[UCLASS](Programming/UnrealArchitecture/Reference/Classes#classdeclaration)(EditInlineNew, Meta=(DisplayName="Distance"), MinimalAPI) class UNiagaraSignificanceHandlerDistance : public [UNiagaraSignificanceHandler](API\Plugins\Niagara\UNiagaraSignificanceHandler)